With a progressive development of display technique, a light-emitting diode (LED) display panel gradually comes into the market, typically comprising an active matrix organic light-emitting diode (AMOLED). Compared with a traditional liquid crystal display (LED) technique, AMOLED display has a faster response speed, a higher contrast ratio and a broader angle of view and does not need any backlight unit. Therefore, AMOLED display is considered as a next generation of display technique. In AMOLED, a light-emitting display is an organic light-emitting diode (OLED). Under a driving of an AMOLED driving circuit, OLED emits light when there is current flowing through the light-emitting device.
Pixel driving circuit of AMOLED generally adopts a 2T1C driving circuit which comprises two thin film transistors (TFT) and one capacitor. One TFT is configured to control writing of a data line voltage Vdata and is called as a switching TFT, the other TFT is configured to control an operating state of OLED and is called as a driving TFT, and the capacitor C is configured to maintain a strobe electrode voltage of the other TFT.
In the 2T1C driving circuit, a threshold voltage of the driving TFT will drift as the display operates for a long time, while light-emitting luminance of OLED is closely related with the threshold voltage. Therefore, a change of the threshold voltage of the driving TFT will greatly influence the light-emitting luminance of OLED. That is, the change of the threshold voltage of the driving TFT will influence luminance uniformity of OLED. In addition, in the process of OLED operation, the driving TFT always keeps in a turn-on state. A long time of operation will reduce lifetime of the driving TFT, and thus reduce lifetime of the OLED display panel.
Therefore, it is desired to improve the driving circuit for driving OLED, so as to solve one or more of the problems described above. That is, it is desired to avoid an effect of the threshold voltage of the driving TFT on the light-emitting luminance of OLED, or to increase lifetime of the driving TFT.